[v8][layout-tests] remove gtest specification from {V8 Blink Win}

This CL removes the gtest_test specification to fix the crashes in
https://ci.chromium.org/p/v8/builders/ci/V8%20Blink%20Win/10

R=machenbach@chromium.org

Bug: chromium:883629
No-Try: True
Change-Id: Ifa84c72601ddabda11cc186784eb25a47cfbbdd9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1741984
Auto-Submit: Tamer Tas <tmrts@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685127}

testing/buildbot/client.v8.fyi.json

@@ -1499,27 +1499,6 @@
     ]
   },
   "V8 Blink Win": {
-    "gtest_tests": [
-      {
-        "args": [
-          "--disable-blink-features=LayoutNG"
-        ],
-        "merge": {
-          "args": [],
-          "script": "//testing/merge_scripts/standard_gtest_merge.py"
-        },
-        "name": "webkit_unit_tests_ng",
-        "swarming": {
-          "can_use_on_swarming_builders": true,
-          "dimension_sets": [
-            {
-              "os": "Windows-7-SP1"
-            }
-          ]
-        },
-        "test": "blink_unittests"
-      }
-    ],
     "isolated_scripts": [
       {
         "args": [
@@ -1538,7 +1517,7 @@
           "can_use_on_swarming_builders": true,
           "dimension_sets": [
             {
-              "os": "Windows-7-SP1"
+              "os": "Windows-10-15063"
             }
           ],
           "shards": 12

testing/buildbot/waterfalls.pyl

@@ -4211,10 +4211,9 @@
       },
       'V8 Blink Win': {
         'mixins': [
-          'win7',
+          'win10',
         ],
         'test_suites': {
-          'gtest_tests': 'layout_ng_gtests',
           'isolated_scripts': 'chromium_webkit_isolated_scripts',
         },
       },